This invention concerns the generation of signals corresponding to the torque produced by an internal combustion engine. The measurement of torque produced by an engine is generally carried out in a test cell using elaborate and expensive equipment and is time consuming. It is difficult to monitor torque under actual running conditions such as in an automobile. Measurement of spring resisted deflections in the drive line of a transmission mechanism have been developed but none of these have been particularly adapted to detect engine torque under running conditions in an automobile.
Internal combustion engines power practically every kind of mobile machine from automobiles, trucks, tractors, tanks, boats, seagoing vessels, airplanes, air compressors, and lawn mowers. Electronic control systems are now extensively used in automobiles to monitor and manage engine functions because they have proven to be cost effective and reliable and have improved the function, performance, reliability, and efficiency of automobile engines in ways unrecognizable even a decade ago. Very few automobiles are produced without a microprocessor on board.
It would be advantageous to provide an engine torque sensing device generating electronic signals during operation of the engine so as to be able to process signals for further use in these microprocessors. For example, when engine torque and engine speed are monitored, they are together proportional to engine horsepower which could then be readily displayed on the instrument panel of a vehicle and could warn the driver, in an open loop system, to carry out a certain function such as changing gears. More importantly, it could in a closed loop system automatically shift the gears of automatic transmissions when working with the other inputs currently employed to improve the efficiency and shift quality.
A torque sensing device could also be adapted to sense the degree of overrun which occurs such as when a diesel truck is descending a hill and the engine overspeeds. A retarder could automatically be activated in conjunction with other inputs to slow down the vehicle.
On farm tractors, torque sensing devices are sometimes used to raise or lower a tillage implement just sufficiently to maintain tractor speeds when the soil or terrain conditions vary. When climbing slopes they can downshift a power shift transmission. The device also senses the torque fluctuations in a power-take-off drive (P. T. O.) and when the crop fed into a forage harvester gets too large, downshifting a power-shift transmission can take place until the adverse conditions pass.
Engine horsepower testing is generally carried out in a test cell and the results obtained often vary from those actually realized in a vehicle because the air intake systems, the cooling systems, and the exhaust systems are seldom similar. An electronic torque device could read out the horsepower actually occurring and would be advantageous in monitoring engines for maintenance tune-ups, classification, and regulatory tests.
For instance, farm tractor P. T. O. power and drawbar horsepower are checked at the University of Nebraska test station at Lincoln before the tractor can be sold, and also in several other locations around the world. It would be advantageous to be able to read the horsepower at the flywheel and compare it with the P. T. O. horsepower and drawbar horsepower so that the drive line efficiencies could be determined. In the field, the overall work efficiency could be continuously monitored by comparing the flywheel horsepower with the drawbar horsepower which can be easily measured when pull type implements are coupled to the tractor drawbar.
Torque sensing during engine running as described could be used to improve the function and efficiency of a wide variety of machinery which is power driven by internal combustion engines to an extent not possible today.
Further, U.S. Pat. No. 4,592,241 describes elastic blade type members to transmit torque between a first rotating member and a second rotating member, and these members are shown mounted singly in close fitting slots at both their inner and outer ends. This arrangement would cause the springs to bind in the slots and cause severe fretting corrosion at the end of each spring and where they exit the slots due to the radial movement occurring during deflection under torsional loads. They can also tilt sideways and bind causing more friction. Further, the deflection of these members would be extremely small and difficult to accurately detect. Also, the binding of the spring members in the slots during loading and unloading of the springs would cause high hysteresis and would not result in a straight line relationship between torque and angular deflection of the flywheel pieces as shown in FIG. 4 of the patent. Embodiments shown in FIGS. 5-8 of that patent would result in even smaller deflections for the detectors to pick up.
U.S. Pat. No. 4,135,390 attempts to signal engine torque by having a pair of detectors measuring the differential in movement at the inner and outer ends of a series of spokes formed in the face of a flex plate connecting an internal combustion engine to the torque convertor housing of an automatic transmission. As with the embodiments in U.S. Pat. No. 4,592,241, the deflections under the sensors are extremely small and parasitic forces caused by temperature variations would cause inaccurate torque signals to be sent to the microprocessor.
The object of the present invention is to provide engine torque sensing by an arrangement incorporated into the engine-transmission drive connection which overcomes the disadvantages of the arrangement shown in U.S. Pat. Nos. 4,592,241 and 4,135,390.